PubMed Health⌕ Search

Biomedical subjects

R J Bernacki

Publications and source records attributed to R J Bernacki.

At least 37 records · Page 2Linked to original sources
PubMed1996

Inhibition of human HT-29 colon carcinoma cell adhesion by a 4-fluoro-glucosamine analogue.

Cell surface glycoconjugates play an important role in cellular recognition and adhesion. Modification of these structures in tumour cells could affect tumour cell growth and behaviour, including metastasis. 2-Acetamido-1,3,6-tri-O-acetyl-4-deoxy-4-fluoro-alpha-D-glycopyranose (4-F-GlcNAc) was synthesized as a potential inhibitor and/or modifier of tumour cell glycoconjugates. The effect of this sugar analogue on the adhesive properties of human colon carcinoma HT-29 cells was evaluated. Treatment of HT-29 cells with 4-F-GlcNAc led to reduced cell surface expression of terminal lactosamine, sialy-Le(x) and sialyl-Le(a), as determined by Western blotting and flow cytometry. The aberrant expression of these oligosaccharide structures on the HT-29 cell surface resulted in: (1) decreased E-selectin mediated adhesion of human colon cells to human umbilical cord endothelial cells (HUVEC); (2) impaired adhesion of HT-29 cells to beta-galactoside binding lectin, galectin-1; and (3) reduced ability to form homotypic aggregates. After exposure to 4-F-GlcNAc, lysosomal associated membrane proteins (lamp) 1 and 2, and carcinoembryonic antigen (CEA) detected in HT-29 cells were of lower molecular weight, probably due to impaired glycosylation. These results strongly suggest that modification of tumour cell surface molecules can alter tumour cell adhesion and that tumour cell surface oligosaccharides may be suitable targets for therapeutic exploitation.

Blotting, Western↗
PubMed1995

Cytotoxicity, cellular accumulation and DNA binding of oxaliplatin isomers.

Oxaliplatin (trans-l-1,2-diaminocyclohexane oxalato Pt(II); 1R,2R-dach, l-OHP), its trans-d isomer (1S,2S-dach) and cis-dach (1R,2S-dach) isomers were compared in in vitro testing against human ovarian carcinoma cell lines A2780, A2780/CP (cisplatin resistant), A2780/l-OHP (oxaliplatin resistant), colon carcinoma cell line HT-29, and murine leukemia cell lines L1210, L1210/CP (cisplatin resistant), and L1210/dach (tetraplatin resistant). The relative molar potency of the three complexes in all the cell lines except A2780/l-OHP and L1210/dach are trans-l > trans-d > cis-dach; in A2780/l-OHP they are trans-l = trans-d > cis-dach; in L1210/dach trans-l > trans-d = cis-dach. The A2780/l-OHP selected for trans-l resistance is 3.6-fold resistant to oxaliplatin, showed no resistance to trans-d isomer and is 6-fold resistant to cis-dach. However, L1210/dach which is selected for carboxyphthalato 1,2-dach (trans-dl) platinum(II) is 140-fold resistant to oxaliplatin, 73-fold resistant to trans-d, and 41-fold resistant to cis-OHP. The accumulation and DNA binding of platinum following a 2-h treatment of A2780 cells with each of the isomers (60 microM) is in the order of trans-l > cis-dach > trans-d which corresponded to the cytotoxicity of trans-l, but not the others. The data suggest that other processes, such as differential formation of specific adducts and/or repair may be involved. Of the three isomers l-OHP is the superior and its accumulation and DNA binding are consistent with its cytotoxicity.

Animals↗
PubMed1995

Versatile intermediates in the selective modification of the amino function of 2-amino-2-deoxy-D-mannopyranose and the 3-position of 2-acetamido-2-deoxy-D-mannose: potential membrane modifiers in neoplastic control.

A general method has been developed to selectively modify the amino group of 2-amino-2-deoxy-D-mannopyranose (D-mannosamine), a precursor of the terminal membrane sugar, sialic acid. 1,3,4,6-Tetra-O-acetyl-2-amino-2-deoxy-alpha-D-mannopyranose oxalate was prepared via two routes that allowed introduction of various acyl groups onto the amino function. These compounds were evaluated for their antineoplastic properties. The most significant preclinical therapeutic finding was the antileukemic activity found in mice for tetra-O-acetyl-2-epi-streptozotocin (the acetylated alpha-mannosamine epimer of streptozotocin). Administration of 50 mg/kg/day x 5 to leukemia L1210-bearing DBA/2Ha mice resulted in 5/5 35-day survivors. Neutralization of 1,3,4,6-tetra-O-acetyl-2-amino-2-deoxy-alpha-D-mannopyranose oxalate under aqueous conditions led to 2-acetamido-1,4,6-tri-O-acetyl-2-deoxy-alpha-D-mannopyranose, the oxidation of which gave 2-acetamido-4,6-di-O-acetyl-1,5-anhydro-2-deoxy-D-erythro-hex-1-en-3- ulose. This agent demonstrated an IC50(2) of 25 microM with a murine L1210 cell culture. Administration of 100 mg/kg/day x 5 resulted in 42% ILS3 in DBA/2 mice with ip L1210 leukemia. Several other nonacetylated derivatives were also prepared by direct N-acylation, producing, for example, fluorescently tagged N-dansylmannosamine.

Animals↗
PubMed1995

Antitumor efficacy of taxane liposomes on a human ovarian tumor xenograft in nude athymic mice.

Taxanes such as paclitaxel (Taxol) and docetaxel (Taxotere) are promising agents for use against ovarian cancer and other malignancies. Recently, SB-T-1011, a semisynthetic taxane, has been prepared from 14-hydroxy-10-deacetylbaccatin III. SB-T-1011 shows similar or greater in vitro cytostatic activity than paclitaxel, depending on the tumor cell line. The administration of taxanes is problematic due to their low solubility in most pharmaceutically acceptable solvents; formulations used clinically contain Cremophor/ethanol (diluent 12) or polysorbate 80/ethanol, excipients which may cause serious adverse effects. To eliminate these vehicles, we have prepared paclitaxel liposome formulations. The objective of the present work was to evaluate the antitumor activity of paclitaxel and two semisynthetic analogs in Cremophor-based and liposomal formulations. Antitumor activity was evaluated against A121a, a taxane-sensitive human ovarian tumor, growing as subcutaneous xenografts in athymic nude mice. Free and liposomal formulations of each taxane showed similar antitumor effect. The antitumor activity of paclitaxel and SB-T-1011 was similar, and docetaxel was more potent than either paclitaxel or SB-T-1011. Overall, taxane liposomes were better tolerated and more easily administered iv than taxane formulated in Cremophor/ethanol.

Animals↗
PubMed1995

Preclinical antitumor efficacy of the polyamine analogue N1, N11-diethylnorspermine administered by multiple injection or continuous infusion.

Certain N-alkylated analogues of the natural polyamine spermine have been found to disrupt polyamine pool homeostasis and inhibit tumor cell growth. The most effective of these analogues, N1, N11-diethylnorspermine (DENSPM), apparently depletes intracellular polyamine pools primarily by inducing the polyamine acetylating enzyme spermidine/spermine N1-acetyltransferase, which contributes to polyamine depletion via increased polyamine excretion and catabolism. In this report, the experimental therapeutic efficacy of DENSPM was further examined with the use of other human solid tumor xenografts, including A121 ovarian carcinoma, A549 lung adenocarcinoma, HT29 colon carcinoma, and SH-1 melanoma, and compared with previously obtained findings with MALME-3M and PANUT-3 human melanomas. In vitro studies indicated that the growth sensitivity of most tumor cell lines to DENSPM was similar, with characteristically flat dose-response curves and IC50s ranging between 0.1 and 1 micrometer the only exception was the HT29 colon carcinoma cell line, which had an IC50 of >100 micrometer. For in vivo studies, DENSPM was administered by i.p. injection to female nude athymic mice at 40 and/or 80 mg/kg 3 times a day (every 8 h) for 6 days or by continuous s.c. infusion with the use of Alzet pumps at 120, 240, or 360 mg/kg/day for 4 days. Treatment began after s.c. tumor xenografts had reached 100-200 mm3. The SH-1 melanoma, A549 lung adenocarcinoma, and A121 ovarian carcinoma xenografts responded well to the i.p. administration of analogue with obvious tumor regressions, long-term tumor growth suppressions, and a significant proportion (up to 40%) of apparent cures (i.e., lack of tumor regrowth). However, in similarity to in vitro findings, HT29 colon carcinoma xenografts responded poorly to DENSPM treatment. Massive induction of N1-acetyltransferase activity and extensive depletion of polyamine pools were consistent findings in most tumor types after in vivo or in vitro treatment with DENSPM. The rapidly growing human LOX melanoma xenograft, however, demonstrated poor induction of N1-acetyltransferase activity and the poorest response to DENSPM treatment. In nude athymic mice with MALME-3M melanoma xenografts, constant infusion delivery of DENSPM resulted in prolonged inhibition of tumor growth and long-term tumor regressions comparable to those produced by multiple i.p. injections. On the basis of the unique structure of DENSPM, novel target and mode of intervention, mild host toxicity, and activity against different human solid tumor xenografts, DENSPM is currently being developed as an antitumor agent in humans.

Adenocarcinoma↗
PubMed1994

Inhibition of lectin-mediated ovarian tumor cell adhesion by sugar analogs.

Adhesion of A-121 human ovarian carcinoma cells to extracellular matrix is partly mediated via interaction between galaptin, an endogenous beta-galactoside-binding lectin present in extracellular matrix, and specific cell surface carbohydrate receptors identified as lysosomal associated membrane proteins, lamp-1 and lamp-2. In this study, we report that adhesion of human ovarian carcinoma cells to polystyrene plates coated with polymerized human splenic galaptin can be inhibited by polyclonal antibodies raised against lamp-1 and lamp-2 molecules and by pretreatment of A-121 human ovarian carcinoma cells with glucosamine analogs: 2-acetamido-1,4,6-tri-O-acetyl-3- deoxy-3-fluoro-alpha-D-glucopyranose (3-F-GlcNAc) and 2-acetamido-1,3,6-tri-O-acetyl-4-deoxy-4-fluoro-alpha-D-glucopyranose (4-F-GlcNAc). A 48-h exposure of A-121 cells to individual sugar analogs, or to a combination of the two, resulted in a concentration-dependent inhibition of cellular attachment to polymerized galaptin. Both drugs inhibited glycoprotein biosynthesis as measured by cellular incorporation of labeled [3H]glucosamine and [3H]fucose with negligible effects on [3H]thymidine and [3H]leucine incorporation and cell growth. As a result of drug action on glycoprotein biosynthesis, an alteration in the structure of the galaptin receptor was noted by indirect immunofluorescence and Western blot analysis. Moreover, probing gels of cell extracts with anti-lamp antibodies or Datura stramonium lectin demonstrated significant changes in the reactivity and pattern of glycoprotein staining, suggesting an effect of sugar analogs on the glycosylation of various cellular receptor molecules. The greatest change was observed when tumor cells were exposed to a combination of the two sugar analogs. These studies suggest that specific endogenous lectins and their surface receptors play a role in tumor cell adhesion and perhaps metastasis and may serve as suitable targets for therapeutic exploitation.

Acetylglucosamine↗
PubMed1994

A biosynthetic control on structures serving as ligands for selectins: the precursor structures, 3-sialyl/sulfo Gal beta 1, 3/4GlcNAc beta-0-R, which are high affinity substrates for alpha 1, 3/4-L-fucosyltransferases, exhibit the phenomenon of substrate inhibition.

The present study reports a control on the biosynthesis of fucosylated structures, serving as ligands for selectins by demonstrating the potential of 3-sialyl or 3-sulfo Gal beta 1, 3/4GlcNAc beta-containing glycoconjugates as high affinity substrates for alpha 1, 3/4-L-fucosyltransferases and as substrate inhibitors at higher concentrations. The synthetic sulfated saccharides and the triantennary sialoglycopeptide from fetuin were potent competitive inhibitors of the transfer of fucose to non-anionic saccharide acceptors and the corresponding triantennary asialoglycopeptide respectively catalyzed by a partially purified alpha 1, 3/4-L-fucosyltransferase preparation from Colo 205 (specific activity:transfer of 113.1 nmol Fuc to 2'-FucosylLacNAc per h per mg protein); Ki for the inhibitions by triantennary sialoglycopeptide, 3-SulfoGal beta 1, 3GlcNAc beta-0-Allyl and a copolymer from 3-SulfoGal beta 1, 3GlcNAc beta-0-Allyl and acrylamide were 51.9 microM, 500 microM and 67.0 microM, respectively. Further, the alpha 1,3-specific anionic acceptor, 3'-SulfoLacNAc, also inhibited the alpha 1,4- activity; Km for the alpha 1,4-specific acceptor, 2-methylGal beta 1, 3GlcNAc beta-0-Bn increased from 0.40 mM to 1.35 mM in presence of 3.0 mM 3'-sulfoLacNAc, whereas Ki for the mutual inhibition of alpha 1,3-activity by the former was found to be high (3.64 mM). Furthermore, the phenomenon of substrate inhibition, serving as acceptors at lower concentrations and as inhibitors at higher concentrations, was exhibited by the anionic acceptors; the Hill plots gave the Ki values 342.7 microM, 13.03 mM and 13.36 mM respectively for fetuin triantennary sialo glycopeptide, 3'-sulfoLacNAc and 3-sulfoGal beta 1, 3GlcNAc beta-0-Allyl.

Asialoglycoproteins↗
PubMed1993

Galaptin-mediated adhesion of human ovarian carcinoma A121 cells and detection of cellular galaptin-binding glycoproteins.

Previously, we have shown that galaptin, an endogenous beta-galactoside-binding lectin, is present in extracellular matrix where it may participate in the adhesion of A121 human ovarian carcinoma cells to extracellular matrix via interaction with specific cell surface carbohydrate receptors. We now report that A121 cells adhere to polystyrene plates coated with polymerized human splenic galaptin. The carbohydrate-mediated specificity of this adhesive interaction was demonstrated by inhibition with lactose. Additionally, treatment of A121 cells with neuraminidase increased cellular adherence by 30%, while beta-galactosidase treatment of cells decreased adherence by 65%. These findings prompted us to isolate and identify the cell surface galaptin receptor. In a Western blot of A121 cell extracts separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, 125I-labeled polymerized galaptin bound [corrected] to a unique cellular protein having a molecular mass of 110 kDa. This receptor was enriched by affinity chromatography using polymerized galaptin-Sepharose. Treatment of this material with N-glycanase ablated its galaptin-binding activity. In related studies, A121 cells metabolically labeled with [3H]glucosamine demonstrated a radiolabeled polymerized galaptin-binding protein with an identical molecular mass of 110 kDa. These studies confirmed the glycoprotein nature of this putative endogenous cellular galaptin receptor. Further studies with antibodies directed against two lysosomal associated membrane proteins, lamp-1 and lamp-2, demonstrated specific reactivity in Western blots with the 110-kDa glycoprotein. Additionally, 125I-polymerized galaptin recognized a 110-kDa protein in Western blots of material immunoprecipitated from A121 cell lysates by lamp-1 and lamp-2 antibodies. Finally, indirect immunofluorescence using antibodies directed against lamps detected cell surface antigenicity. Therefore, lamp-1 and/or lamp-2 appear to be the putative cell surface receptors involved in the adhesion of ovarian carcinoma cells to extracellular matrix mediated by galaptin.

Antigens, CD↗
PubMed1993

Fluorinated carbohydrates as potential plasma membrane modifiers. Synthesis of 3-deoxy-3-fluoro derivatives of 2-acetamido-2-deoxy-D-hexopyranoses.

Treatment of benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-alpha-D-allopyranoside with diethylaminosulfur trifluoride or of the 3-O-mesyl derivative with tetrabutylammonium fluoride gave the 2,3-unsaturated compound instead of the expected 3-deoxy-3-fluoro derivative. The latter was obtained when benzyl 2-acetamido-4,6-di-O-benzyl-2-deoxy-3-O-mesyl-alpha-D-allopyran oside was treated with potassium fluoride. Methyl 2-azido-4,6-O-benzylidene-2-deoxy-alpha-D-altropyranoside was converted into the 2-acetamido- and 2-phthalimido-3-O-mesyl derivatives; when treated with fluoride nucleophile, these gave only the 2,3-aziridine derivative. However, treatment of the 2-azido-2-deoxy derivative with diethylaminosulfur trifluoride gave methyl 2-azido-2,3-dideoxy-3-fluoro-alpha-D-mannopyranoside which, after reduction, deprotection, and acetylation, gave the acetylated derivative of methyl 2-acetamido-2,3-dideoxy-3-fluoro-alpha-D-mannopyranoside in excellent yield. These acetylated 3-fluoro derivatives exhibited inhibition of cell growth of murine L1210 leukemia cells in culture at micromolar concentrations.

Acetylglucosamine↗
PubMed1993

Antitumor activity of N1,N11-bis(ethyl)norspermine against human melanoma xenografts and possible biochemical correlates of drug action.

In in vitro systems, the spermine analogue, N1,N11-bis(ethyl)norspermine (BENSPM), suppresses the polyamine biosynthetic enzymes, ornithine and S-adenosylmethionine decarboxylase (ornithine decarboxylase and S-adenosylmethionine decarboxylase, respectively), greatly induces the polyamine catabolic enzyme, spermidine/spermine N1-acetyltransferase (SSAT), depletes polyamine pools, and inhibits cell growth. Against MALME-3 M human melanoma xenografts, BENSPM and related homologues demonstrate potent antitumor activity that has been found to correlate positively with their ability to induce SSAT activity in vitro. Herein, we further evaluate the antitumor activity of BENSPM and at the same time characterize the biochemical effects of BENSPM treatment on polyamine metabolism of selected normal and tumor tissues. At 40 mg/kg 3 times/day for 6 days i.p., BENSPM suppressed growth of MALME-3 M human melanoma xenografts during treatment and for 65 days afterwards. Similar antitumor activity was obtained with 120 mg/kg once daily for 6 days and 40 mg/kg once daily for 6 days, indicating that against this tumor model, the dosing schedule can be relaxed up to sixfold without compromising antitumor activity. When MALME-3 M tumor-bearing mice were retreated with BENSPM 2 weeks after the first treatment at 40 mg/kg 3 times/day for 6 days, initial tumor volumes of 85 mm3 were reduced to < 10 mm3. Analysis of melanoma, liver, and kidney tissues from mice treated with 40 mg/kg 3 times/day for 6 days revealed relatively similar accumulations of BENSPM in all tissues at levels greater than the original total content of polyamine pools. By 2 weeks following treatment, BENSPM pools in normal tissues were almost gone, whereas in tumor tissues significant amounts (40%) were still retained. The biosynthetic enzymes, ornithine decarboxylase and S-adenosylmethionine decarboxylase, gave no indication of enzyme suppression (or increase) by the analogue as typically occurs in vitro. By contrast, SSAT was induced from an average of < 50 pmol/min/mg in control tissues to 320 pmol/min/mg in liver, 1255 pmol/min/mg in kidney, and 13,710 pmol/min/mg in MALME-3M tumor. Two weeks later, SSAT activity was still 12 times higher in tumor than in kidney. Polyamine pools (putrescine, spermidine, and spermine) were reduced after treatment in all tissues and approached near-total depletion in the tumor. Good antitumor activity and even more potent induction of SSAT (i.e., 26,680 pmol/min/mg) was also observed in PANUT-3 human melanoma xenografts. Overall, the findings reveal meaningful antitumor activity by BENSPM against 2 human melanoma xenografts and provide in vivo evidence consistent with SSAT-induced polyamine depletion playing a determining role in at least the initial phase of the antitumor response.

Acetyltransferases↗
PubMed1992

Antitumor activity of N,N'-bis(ethyl)spermine homologues against human MALME-3 melanoma xenografts.

The spermine analogues, N1,N12-bis(ethyl)spermine (BESPM), N1,N11-bis(ethyl)norspermine (BENSPM), and N1,N14-bis(ethyl)-homospermine (BEHSPM) behave similarly in down-regulating the key polyamine biosynthetic enzymes, ornithine and S-adenosylmethionine decarboxylase, but differ distinctly in their abilities to induce the polyamine catabolic enzyme, spermidine/spermine-N1-acetyltransferase; BENSPM is 6-fold more effective than BESPM in increasing spermidine/spermine-N1-acetyltransferase activity and BEHSPM is 10-fold less effective. Since MALME-3 human melanoma cells are extremely responsive to spermidine/spermine-N1-acetyltransferase induction (i.e., increases greater than 200-fold) and since this induction correlates with growth inhibition among melanoma cell lines, the ability of these homologues to inhibit the growth of MALME-3 xenografts was examined. Analogues were administered i.p. three times per day (i.e., every 8 h) for 6 days at the following doses per injection: BEHSPM, 1.5, 3, or 6 mg/kg; BESPM, 10, 20, or 40 mg/kg; BENSPM, 20, 40, or 80 mg/kg. At the highest tolerated doses, all of the analogues fully suppressed growth of established (100-200 mm3) MALME-3 tumor during treatment and sustained tumor growth inhibition following treatment as follows: BEHSPM, 14 days; BESPM, 27 days, and BENSPM, 37 days. The tumor delay (to reach 1000 mm3 relative to control) at the highest tolerated doses was as follows: BEHSPM, 20 days; BESPM, 34 days, and BENSPM, 63 days. The rank order of analogue host toxicity as indicated by weight loss was opposite that for antitumor activity, BEHSPM was most toxic, BESPM, intermediate, and BENSPM, least toxic. Thus, the most effective of the three homologues, BENSPM, was best tolerated, and produced an initial tumor regression, full suppression of tumor regrowth during treatment, and sustained inhibition of tumor regrowth for 37 days after treatment stopped. Owing to its potent antitumor activity, mild host toxicity, and novel apparent mechanism of action, BENSPM is being considered for further development toward clinical trial.

Acetyltransferases↗
PubMed1991

1-beta-D-arabinofuranosylcytosine conjugates of ether and thioether phospholipids. A new class of ara-C prodrug with improved antitumor activity.

The 1-beta-D-arabinofuranosylcytosine (ara-C) conjugates 1-O-alkyl (ether) and 1-S-alkyl (thioether) phospholipids, being analogues of ara-CDP-sn-1,2-O-dipalmitoylglycerol (1), showed significant antitumor activity against L1210 and P388 leukemia in vivo. The more active conjugates include the 1-O-alkyl analogues, ara-CDP-rac-1-O-hexadecyl-2-O-palmitoylglycerol (2) and ara-CDP-rac-1-O-octa-decyl-2-O-palmitoylglycerol (3), and the corresponding 1-S-alkyl analogues, ara-CDP-rac-1-S-hexadecyl-2-O-palmitoyl-1-thioglycerol (4) and ara-CDP-rac-1-S-octadecyl-2-O-palmitoyl-1-thioglycerol (5, Cytoros). The conjugates were formulated by sonication, in which the conjugates existed as discs (size 0.01-0.04 microns). Among the conjugates of the three different phospholipids, the 1-S-alkyl analogues 4 and 5 displayed the strongest antitumor activity against L1210 leukemia in mice, followed by the 1-O-alkyl (2 and 3) and the 1-O-acyl (1) analogues. The 1-S-alkyl analogue 5 was considerably more effective than the 1-O-acyl analogue 1 against myelomonocytic WEHI-3B leukemia in mice. Conjugate 5 (Cytoros) showed a significant therapeutic activity in mice with colon 26 carcinoma, M5076 sarcoma, and C-1300 neuroblastoma. Furthermore, this agent inhibited liver metastases of M5076 sarcoma. Conjugates 3 and 5 also inhibited the metastasis of 3-Lewis lung carcinoma to the lungs of mice. Cytoros (5) and its analogues, with other ether and thioether phospholipids, appear to offer increased therapeutic benefit to mice with tumors.

Analysis of Variance↗
PubMed1991

Effects of doxorubicin on the sensitivity of L1210 leukemia cells to deformation-associated trauma.

Most of the cancer cells arrested in the microcirculation during hematogenous metastasis are rapidly killed; one major mechanism is surface-membrane rupture, associated with the mechanical deformation of cancer cells in capillaries. The feasibility of increasing the susceptibility of cancer cells to lethal, deformation-associated trauma by doxorubicin, was tested in an in vitro mechanical model system, by filtering suspensions of L1210 leukemia cells through 8-microns pore-size Nuclepore membranes, with or without prior incubation with 10(-7)M doxorubicin. The results showed that mechanically-induced loss of cancer cells immediately after filtration was increased from 18 to 55% in cells previously exposed to doxorubicin for 48 h. The results indicate the feasibility of chemotherapeutic enhancement of the mechanical killing-action of the microvasculature as a potential rate-regulator of hematogenous metastasis.

Animals↗
PubMed1991

Targeting 5'-deoxy-5'-(methylthio)adenosine phosphorylase by 5'-haloalkyl analogues of 5'-deoxy-5'-(methylthio)adenosine.

A series of 5'-haloalkyl-modified analogues of 5'-deoxy-5'-(methylthio)adenosine (MTA), a nucleoside byproduct of polyamine biosynthesis, has been synthesized: 5'-deoxy-5'-[(2-monofluoroethyl)thio]adenosine (10), 5'-deoxy-5'-[(2-chloroethyl)thio]adenosine (4), 5'-deoxy-5'-[(2-bromoethyl)thio] adenosine (5), and 5'-deoxy-5'-[(3-monofluoropropyl)thio]adenosine (13). On the basis of their abilities to serve as substrates of MTA phosphorylase prepared from mouse liver, several of these analogues were characterized for their growth inhibitory effects in MTA phosphorylase-containing (murine L5178Y and human MOLT-4) and MTA phosphorylase-deficient (murine L1210 and human CCRF-CEM) leukemia cell lines. The MTA phosphorylase-containing tumor cell lines, especially of human origin, were found to be more sensitive to treatment by these analogues. Of the analogue series, 10 was the most potent inhibitor of growth in each of the cell lines tested. The analogues, especially compound 10, displayed a reduced capacity to alter polyamine pools relative to MTA, mechanistically indicating a decreased potential for interactions at sites other than MTA phosphorylase. The results indicate that of the analogues tested, compound 10 displayed the best inhibitor/substrate interaction with MTA phosphorylase, which, in turn, correlated with more potent growth inhibition in tumor cell lines containing MTA phosphorylase. Overall, this supports the concept that MTA phosphorylase plays a role in the activation of such analogues.

Adenosine↗
PubMed1990

Formulation, stability, and antitumor activity of 1-beta-D-arabinofuranosylcytosine conjugate of thioether phospholipid.

1-beta-D-Arabinofuranosylcytosine 5'-diphosphate-rac-1-S-octadecyl-2-O- palmitoyl-1-thioglycerol (ara-CDP-DL-PTBA) is an effective stable 1-beta-D-arabinofuranosylcytosine (ara-C) conjugate of thioether phospholipid against a variety of transplantable tumors in mice. The conjugate was formulated in a micellar solution by sonication, in which the conjugate exists as micellar discs (size, 0.01 to 0.04 micron). Analyses on thin-layer and high-pressure liquid chromatography showed that the conjugate was chemically stable upon storage at 3-4 degrees C for more than a 6-mo period. However, stored at room temperature for 3 mo it began to degrade (3 to 11%) to 1-beta-D-arabinofuranosylcytosine 5'-monophosphate and phosphatidic acid. At 3-4 degrees C, the micellar structure remained generally unchanged for 6 mo (size, less than 0.1 micron). Samples stored for 4 mo at room temperature formed some larger vesicles (size, 0.1 to 0.4 micron). Antitumor activity against i.p. implanted L1210 leukemia in mice remained relatively constant with samples stored for 6 mo at 3-4 degrees C or 3 mo at room temperature. 1-beta-D-Arabinofuranosylcytosine 5'-triphosphate (ara-CTP) levels were elevated (greater than 500 pmol/10(7) cells) in L1210 leukemia cells within 1 h following i.p. administration of 400 mg/kg of ara-CDP-DL-PTBA to mice. More importantly, retention of cellular ara-CTP was prolonged (greater than 24 h) in these tumor cells as compared with ara-C treatments. Administration of ara-CDP-DL-PTBA to mice with colon 26 carcinoma (s.c.) resulted in both significant antitumor activity with an increased life span greater than 100% and decreased tumor size. The conjugate also demonstrated a dose-dependent therapeutic effect in mice with M5076 sarcoma (s.c.) as demonstrated by decreases in tumor size and liver metastases. Overall, ara-CDP-DL-PTBA, a stable lipid conjugate of ara-C in a micellar solution, appears to offer substantial therapeutic benefit to mice with leukemia and solid tumors warranting its further development and clinical investigation.

Animals↗